Spray a 9 x 13” pan with nonstick cooking spray. Line the bottom with parchment paper. Sprinkle a heavy layer of confectioners’ sugar over the parchment paper.
Soften the gelatin by placing the ½ cup cold water into a small bowl and sprinkling the powdered gelatin over it. Stir briefly and allow it to bloom and solidify.
In a heavy medium saucepan, combine the sugar, corn syrup and 1/3 cup water. Bring the mixture to a boil stirring just until the sugar is dissolved. Wash down any sugar crystals with a pastry brush dipped into water.
Cook the mixture until a candy thermometer climbs to 240°F.
While the sugar syrup is cooking, place the egg white into the bowl of an electric mixer. Using the whip attachment beat the egg white until it forms stiff peaks.
Once the sugar syrup reaches 240°F, gently place the softened gelatin into it, and whisk until it has melted. Remove the mixture from the heat and pour it into a greased, heatproof liquid measuring cup.
With the mixer on medium speed, slowly pour the sugar syrup into the beaten egg white (do not pour the syrup directly onto the beaters).
Once the sugar syrup has been added, turn the mixer up to high speed. Add the vanilla extract.
Continue beating until the mixture looks light and fluffy.
Using a rubber spatula, pour the marshmallow into the 9 x 13” pan spreading the mixture evenly.
Allow the marshmallow to sit at room temperature for several hours until firm.
Gently remove the marshmallow from the pan. Place on a cutting board. Using a knife sprayed with nonstick cooking spray, cut the marshmallow into squares, rectangles or using a cookie cutter into any shape you wish. Roll each marshmallow into confectioners’ sugar.
Place cut marshmallows onto a sheet pan lined with waxed paper sprinkled with confectioners’ sugar.
Store at room temperature in an airtight container separated by layers of wax paper for one week.